I google'd "hide on screen buttons android" and got quite a few results, but haven't the time to read through them (plus, I don't mind having the buttons there). I'm guessing that if you rooted the phone and installed a custom ROM, a number of them would have this feature. Things like this are one of the primary reasons to root and ROM your phone...to make it work like you want it to. If you haven't already, you might want to at least unlock your bootloader now. It will completely wipe everything on your phone (though you only do this once in the life of your device), including anything on your virtual sd card. If you decide to root/ROM later, you wont loose all the stuff that you've accumulated over the months of having it.